Balance testing mechanism



R. D. SMITH BALANCE TESTING MECHANISM May 30, 1944.

Filed May 5, 1942 2 Sheets-Sheet 2 Snuentor Cttorneg Patented May 30, 1944 BALANCE TESTING MECHANISM Roy nl smith, Betteaorf, iowa, 'assignorto Bee- Line Company, 'Scotti County, Iowa,`a copartnership Application May 5, 1942, semi No. 441,883'

Y 11 Claims. (Cl. vs -'53) In the art of testing the balance of airplane propellers and other bodies rotating at al high speed, there have heretofore been vno means proe vided for making an accurate t'est of the balance or'unbalance of the article which it is desired to have accurately balanced. As a result, there have been inaccuracies in the balance of such structures which have resulted in lateral vibration thereof and of the shaft supporting the same for rotation. This results in excessive wear of the shaft bearings and eventually necessitates extensive repairs to the machine with which such rotating body is connected. 'I'he principal ob'- ject, therefore, of the present invention is to provide an apparatus by means of which `minute deviations from a perfect balance may befdiscovered in the structure being tested. Other objects are to provide an'accurate apparatus for the purpose indicated which is inexpensive to` produce; to provide a structure of the. character indicated which will produce accurate'results and yet will not be so sensitive as to be practically impossible to manufacture; to provide a structure for the purpose indicated in which the location of the center'of mass of a supported system can be readily adjusted vertically whereby to regulate the sensitivity of the testing apparatus; and such further objects, advantages, land capabilities as' will hereafter appear and as are inherent Ain the structure disclosed herein. My invention further resides in the combination, construction, and arrangement of parts illustrated in the accompanying: drawings and, while I have shown therein wha'tis now regarded as the preferred embodiment of this invention, I desire the same to be understood as illustrative only and not to be interpreted in a limiting sense. f In the drawings annexed hereto and parthereof,

Fig. lrepresents, essentially, a vertical `central sectionof this apparatus `with a propeller mounted thereon, parts of the propeller being broken away;

Fig. 2 represents a vertical transverse section approximately along the broken plane indicated by the line 2 2, Fig. 1;

Fig. `3 ,represents a fragmentary longitudinal section of the hub part of a different type of propeller applied to this apparatus for balance test-1 ing? and l Fig. 4 represents a horizontal cross-section substantially along the `plane indicated bythe line ll--IL Fig. 1.

Reference will now be made in greater detail to the annexed drawings for a more complete` forming a .face I9 constitutes a part.

description of this invention. A support, in the form of a housing I, contains a pump 2 land a variable speed electric motor 3v for driving the pump. This support rests upon adjustable legs 4. A pairlof receptacles orv reservoirs `Ii'andl are supported on the housing I, the outer Vreceptacle having'an outlet 8 leadingfrom the bottom `part thereof and entering the inlet side of the pump 2: From this pump leads an -outlet pipe 9 which constitutes a part ofthe inletsystem of the inner receptacle l. A pipe I0 is connected in fluidtight relation to the `pipe 9 and also toa plate I'I secured to the bottom-of the receptacle I. These two may be held together in fluid-tight relation by bolts I2, as shownin Fig. 1. ,l

A ring I3 fits 'closely the inside of the outer receptacle or reservoir 6 and has a plurality of openings I4 therethrough to permitliquid forced through and out of the receptacle or reservoir 'I to drain back into the receptacle 6. This member I3, in conjunction with the pipe I0, holds the inner receptacle `I againstany movement within the outer receptacle. An extension I5 is'secured to the upper outer portion of the receptacle 'I and the intention is that its upper edge be level when the mechanism is properly leveled up. When the liquid,` preferably oil, with whichthe reservoirs are provided, is forced b-y the pump 2 to overow the top of the extension I5, this liquid flows downwardly through the openings I4 into the chamber in the bottom of the receptacle B. A partition member I6 extends across the upper part of the receptacle 'I and fits closely therein, being Vprovided with openings I'I through which the liquid forced into the lower part of the receptacle "I,

through the tube III, may pass into the upper part ofthe receptacle 'I. These openings I'I, being formed vertically through the partition IIi,` prevent any tendency toa swirling action ofthe liq- V uid entering the upper portion of this receptacle. Vanes IEa assist in preventing swirling action in the liquid passing through the openings I'I.

At the upper edge ofthe `upright wall of the receptacle I is `formed a surface I9 which is a seg- I ment of al spherical surface of which the radius is preferably aboutthirteen and'one-half inches (13% and the center islocated in the axial line of the shaft 5. As amatter of fact, when the parts 5 and I8 tilt because of a statically unbal anced weight placed upon the shaft 5, this tilting is about the center of the sphere of which the sur- 'I'he outer edge portion of the valve-like 'member I8, which contacts the surface I9,vis ground to a similar curvature as the latter surface and, therefore when the member I8 tilts, it maintains good contact with the surface I9 all the way around their region of y from enteringeither receptacle. A cover122 has a downwardly .extending flange which surrounds the flange ZI and assists in keeping out deleterious materials. This cover 22 has a downwardly extending sleeve 23 which rests upon the top of the valve-like member I8. The shaft is secured in member I8 and passesupwardly through the l5,

sleeve 23, extending to a substantial. distance above the cover 20. A plurality of sleeves 24, 25,

2S, and 27, of various lengthsA and diameters, are

provided in order to make it possible to adjust the height of the load 28 with reference lto the center of oscillation, referred to above as the center of the'sphere of whichv the surface I9 constitutes aparts' By'using sleeves'of different lengths dbetween rthe'cover Y22 andthe load 23, shown'in the presentV instance as a propeller, the height ofthe v`center of mass of the 'movable body may 'be "varied, Also, by `interchanging the weights (sleeves `2li, 25,' 25, 21)-, substituting a light for a'heavy ora heavy'for a light, the height ofthe center of mass may be varied. It is always desirable `to -keep the 'center of` mass slightly below the sphere vcenter' referred to'above in order tojhave stable equilibrium. If'th'e center'of mass 'and the spherecenter were identi.. cal, therewould Ybe no tendency to maintain vequilibrium. On the other hand', if the center of massivere to be above the sphere center, then there would be a 'clear-case'of unstable equilibrium. Itisltherefore important to keep the center of mass'somewhat' belov'sT the 4sphere center, butthe nearer the` twoapproachthe more sensitive-is the tester. It' is tli'ereforel possible to adjust" thejf'sensitiveness yof 'the"apparatus by proper selectionv and positioningof the sleeves 24,25, 26",'21',a's'indicated above;

1 Sinc'ethehubs 29 of practically all-propellers are provided witha tapered opening to Vfit aV ta'-v pered` shaft/sleeves 3U are provided,'"'having an' internaldiameter'suchr that they will just .t the shaft 5 "and'diife'rent external diameters 'which fit the different s'iz'e openingsin. the various: hubs.

Fortunately, there'are not a" great number of hub ydiameters"and it is thereforenot necessary to providealarge'number of "tapered sleeves. -A nut `3Iis` screwed"on"the 'upper' end portion of the shaft 5 andpressed downwardly against the upper end of'th'e'sleeve 21, by which the pressure isA transmitted tothe hub"29` to hold? the load in'pro'per position" and'r'igid with relation" to the shaft'. The'ipper endof the shaft, as

shown at 32,A tapered to fit vclosely in'a socket' i two bladeseite'n'ding'in opposite'directions from a center, 'itfi's V-easy v'tddetern'iine the direction of oifbal`ance;v."Onfth other hand, if'there are three .bladesv extending away 'fromthe axis', lthen itis'necessarytoltum thefcrossbar 33 to rthree different positionsin whichr it'linesup `with' thel `found sensitive to one one-thousandth of an ounce on the tip of a propeller having a circle of rotation two hundred inches (200) in diameter.

Since it is necessary that the valve-like member 4I8 be 'capable of sliding easily on the surface ..IV9, vit is necessary that it and the load supported thereon'shallbe lifted sufficiently to permit a thin film 'of oil to pass between member i3 and the surface I9. If the pump 2 is not operating, then member I8 settles down upon the surface i@ .and does not slide easily thereon. However, when the motor 3 is started and the pump 2 .draws oil from.,th'e. reservoir 6 and forces it through the pipes 9 and Iilinto the reservoir "I, tliftsv up onethe member I8 and raises this suf-y ciently toipermit a thinV film of oil to pass outwardlythereunder. This makes it possible 'for :the load, comprising the member I8 and all parts supported thereby, to""seek a position of equilibriumbytiltin'g about the sphere center. ifthe load is not in a condition of equilibrium. However, -f it is perfectly balanced, it .will not tilt and the bubble of the level 35 will remain in central position.' If a condition of unbalance is indicated byl the llevel, then suicient weight is added to the light part'of the propeller to produce a condition of balance.v Weight may be added to or'.".re1novedV from the' propeller4 or balancing weights maybe adjusted within the hub.

Since propellers vary considerably in weight, itis obvious that it will require various lifting forces to llift the' valve-like member I8 from its seat. Thisfva'riable lifting force can be provided by operating the' motor'3' at different speeds. For this purpose; adjusting means 36 is :provided for rotating the eld of` themotor and varying the-speedvthereof. #When -a sufficient speed vis obtained, thel pressure of the oil on the under face `of the valve-like member I8 will Alift this and its loadsuffcientlytopermit easy tilting thereof in order to produce a condition of balance. Then, by turning the' crossbar' 33 about the shaft 5 until a maximum deflection' of thev level bubble is attained/the' necessary point for adjustment of vthe' load'can be determined. After' thisad-' justment has been made, :a new test can be car-V ried out to determine whether or`not an exact balancehas been attained.

In Fig. 3 is shown another'type 'of propellerhub in which only the ends of the shaft opening'are tapered. This requires the use of a pair of'c`entering members 36which have their end'portions tapered to t the tapered openings in the hub '31.

It will be understood that the tester can be successfully used without the nut 3| and, as amatter' 'of fact, it is more 'commonly used withoutit than with it. Various modifications 'of the' structured disclosed have been tried,"but these all come within the scope-of this invention. It will of course be understood that the specific description of structure set forth herein vmaybe departed from without departing from the spirit of my in;

vention as expressed'in the following claims: i

Havingnow described my inventiongI claim: A

1. In a balance testing machine, a'liquidfre# c'eptacle having 'a 'second receptacle. therein, a 'liquid `inlet extending through 'the lower .part of the first `receptacle and into the-interior of the second receptacle, the upper portion of th'eflateral wall -fof the second receptacle being formed as a valve seat; a closure member `shaped to `fit said seat closely, ai'verticallyfextendingshaft 'carried thereby, the surface of` the ,valve seat and cooperating surface of the'closure member being formed as segments of spherical surfaces, whereby to permit universaltiltingfoftheiclosure member and the shaft carried thereby withirelation to the seat, the direction of tilt of, the shaft indicating the direction `ef unbalance of Ythe member being tested, means ,forfsecuring on said shaft a member the balancev of which lis` to be testedan outlet from Vvthe .first receptacle, l.liquid pumping means connected to said inlet yand outlet to carry liquid under pressure `from the first lreceptacle to the second receptacle anddeliver it beneath said closure member, and -meansfor indicating the amount of tilt and thereby the amount of unbalance.

2. A balance testing mechanism comprising, in combination, a liquid pumping mechanism, a reservoir for liquid connected operatively therewith, a second reservoir within the rst reservoir and spaced laterally therefrom, the second reservoir being connected to the pumping mechanism by a tubular means to carry liquid from the pumping mechanism to the second reservoir, the second reservoir having an open top and being provided with an upwardly directed seat, a valve-like member shaped to fit said seat and resting thereon, a

shaft rising from said valve-like member and` vpassing outwardly from said reservoir, means for securing about said shaft an article to be balanced, said seat and valve member being shaped to allow universal tilting of one with relation to the other whereby to indicate 'the direction of unbalance of said article mounted on said shaft, and level testing means to indicate the amount of unbalance of the article being tested.

3. In a balance testing mechanism, the combination of a pair of liquid receptacles, one within the other and rigidly connected, said receptacles having their upper portions in open communication, liquid pumping means having its inlet connected to the outer receptacle and its outlet connected to the inner receptacle below the top thereof, a valve-like member having a shaft extending upwardly therefrom and out of the tops of the receptacles, the under face of the valve-like member and a face adjacent the upper end of the inner receptacle being fitted to each other comparably to the parts of a ball and socket joint to serve as a valve through which liquid may be forced, securing means connected to the shaft to secure thereto an article, the balance of which is to be tested, and a balance indicating means attachable to said shaft to indicate the deviation from a condition of balance of said article.

4. In a balance testing mechanism, the combination of a pair of liquid receptacles, one within the other and rigidly connected, said receptacles having their upper portions in open communication, liquid pumping means having its inlet connected to the outer receptacle and its outlet connected to the inner receptacle below the top thereof, a valve-like member having a shaft extending upwardly therefrom and out of the tops of the receptacles, the under face of the valvelike member and a face adjacent the upper end of the inner receptacle being fitted to each other to serve as a valve through which liquid may be forced, said faces being similarly curved in the direction of the axis of the valve seat, whereby to permit universal movement of the valve-like member with relation to the seat, vand a level indicatingfmeansconnected-to said shaft to indicate its direction with relation to a vertical line, Whereby to indicate any condition of unbalance of` an article I mounted upon said shaft Vand secured thereto. i

5. In a balance testingfmechanism, the combination of `a pair offliquid-receptacles, one within the other and rigidly connected, said'receptacles having their upper portions in open communication, liquid pumping meanshaving its inlet con-- nected to the outer receptacle' and its outlet connected to the inner receptacle below the top thereof, a valve-like member having a shaft extending upwardly therefrom and out of the tops `of the receptacles, `the under face of the valve-like member and a face adjacent `the upper end of the inner receptacle being` tted to each other to serve as a `valve through which liquid may be forced, meansfor securing to said, shaft an article .to be balanced, said faces being fitted to each other for universal tilting, whereby a condition of unbalance of said article may be determined, and means for determining the amount of such unbalance.

6. In a balance testing mechanism, a, motordriven liquid pump, a variable speed motor for driving said pump, a receptacle to which the inlet of said pump is connected, a second receptacle within the first receptacle, a liquid connection from the outlet of said pump to the interior of the second receptacle below the top thereof, the second receptacle having adjacent its top a valve seat surface, a valve member resting against the valve seat surface and fitting the same closely whether the valve member axis is coincident with or deviates slightly from the axis of the valve seat, a support rising centrally from the valve member and serving as a support for a member to have its balance tested, tilting of said support indicating unbalance of said member, and automatically functioning indicating means to indicate the amount of unbalance of said member.

7 A balancetester comprising a pair of receptacles, one contained within the other, means for drawing liquid from one receptacle and forcing it into the other, the receptacles being spaced from each other, laterally, to permit liquid flowing from the inner receptacle to flow downwardly between the receptacles into the outer receptacle, means within the inner receptacle to prevent a swirling motion of the liquid as it approaches the top of that receptacle, a valve member in the upper part of the inner receptacle, a supporting shaft extending upwardly from said valve member to support the member being tested, tilting of said shaft indicating a condition of unbalance of said member being tested, means on said shaft to secure the member being tested to said shaft, a valve seat on the Wall of the inner receptacle with which the valve member cooperates in holding the liquid from flowing through the valve when the first mentioned means is not functioning, the pressure of the liquid in the inner receptacle, when the rst mentioned means is functioning, serving to lift the valve member from its seat, whereby to permit the liquid to rise in the inner receptacle and overflow into the outer receptacle, the contacting faces of the valve member and seat being segments of a spherical surface whereby to permit easy tilting of the valve member, and an automatically functioning indicating means to indicate the amount of unbalance of said member being tested.

8. A structure as defined by claim 7 in which the upper edgeof the inner receptacle rises :above the valve member sufliciently to'keep the valve member always immersed in liquid.

9. A structure as dened by claim 7 in which the contacting faces of the valve and seat forming segments of a spherical surface have a center of curvature on the axis ofthe shaft and a radius of approximately thirteen and one-half inches(131/2"). T

10. A structure as dened by claim 7 having means for raising and lowering the center ofmass of the supported body and its load. f

11. In an apparatus for the purpose indicated, a pair of containers'` or reservoirs, one within the other,fand both opening upwardly, conduit means connecting the bottom portions of said containers, rigidly, the inner' container having adjacent its upper edge a surface which is a segment of 'a substantially spherical surface, a support having a correspondingly shaped surface cooperating with the rst mentioned surface, an' object-supporting standard `rising approximately vertically from the center of said support, sand standard being designed to support an object substantially symmetrically with relation to the standard, a liquid in said containers, sufcient in amount to ll the inner container and approximately ll the" outer container, and a diaphragm Vwithin the inner contaner, said diaphragm extending across the interior of the inner container and the major part thereof being perforated for the passage of liquid therethrough, in courses substantially'parallel to the axis of the inner container, the liquid, when forced into the inner container, pressing substantially vertically against said support to raise it from contact with the inner container, and the spherical surfaces of contact allowing movement between the support and the inner container, substantially unrestrained by any contact between them. v

ROY D. SMITH. 

